class Phone:
    __is_5g_enable = True
    def __check_5g(self):
        if self.__is_5g_enable == True:
            print ("5g开启")
        else:
            print ("5g关闭，使用4g网络")
            
    def call_by_5g(self):
        self.__check_5g()
        print("正在通话中")   
phone = Phone()
phone.call_by_5g()